Generally the selection of materials for electrical terminals depends upon the sort of connectors in which the terminals are used and the type of electrical equipment onto which the connectors are applied. For instance, copper terminals having very high electrical conductivity are used for power-connecting connectors which are required to have low electrical loss and little temperature increase.
However, copper terminals have a disadvantage in that one mechanical property especially, relatively low resilience, is inferior because of the low limit of elasticity of copper; although the electrical properties of copper are excellent compared to terminals of other materials. Therefore, in the use of a copper terminal where high resiliency is required, for example a female terminal of copper which is required to engage a male terminal and maintain a steady contact pressure even after repetitive insertion of the male terminal, it has recently become the practice to use leaf springs punched out from highly resilient sheet metal to be put upon the electrical terminal as back-up members which help to maintain the contact pressure.